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The structure and chemical composition of boundary layers built under tribological stress affect the friction and wear of solid-state surfaces in a major way. Therefore, information about the chemical composition of the outermost surface and boundary layer are of great importance. Preliminary time of flight secondary ion mass spectrometry (ToF-SIMS) investigations have shown that metal surfaces that have been immersed at high temperatures in phosphonium phosphate-containing oils contain at least some characteristic signals for phosphate containing anti-wear layers. The purpose of this work is to investigate the influence of additive concentration and oil temperature on the formation of phosphate containing layers.

To investigate the formation of phosphate containing layers as a function of temperature, samples of rolling bearing steel 100Cr6 were first heated in a furnace to selected temperatures of 200, 300, 400 and 500 °C, respectively. Then, they were immersed in a model fluid containing ionic liquids as additive in PAO-2 and analysed by ToF-SIMS.

100Cr6 surfaces immersed in trihexyltetradecylphosphonium bis(2-ethylhexyl)phosphate additive oil show characteristic signals of phosphate-like layers at temperatures of 400-500 °C. In addition, characteristic surface signals show a decrease in these ionic liquids at these temperatures.

Ionic liquids could be an alternative to zinc dialkyldithiophosphates as an oil additive. Targeted investigations under friction load could provide information on whether wear-reducing layers are formed.

The peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-10-2019-0436

The purpose of this paper, an R&D project, is to select Globally Harmonized System of Classification and Labeling of Chemicals (GHS)-unclassified white solid lubricants for formulating special lubricating oils, greases and pastes to prevent tribological systems against fretting wear.

The scientific methodology reads as follows: market research to select appropriate additives according to the purpose of the R&D project; screening tests to determine the technical performance of the additives; advanced technical studies and tests to validate the technical performance of the lubricating additives; determination of the reaction layers; and clarification of the build-up mechanism of the reaction layers (practical tests).

The findings of the R&D project can be summarized as follows: the selected white solid lubricants perform in lubricating oils, greases and pastes highly effective against fretting wear. The performance could be shown on the basis of representative test results and highlights its advantages compared to the state of the art.

The research team faced some challenges during the R&D project – the unsuitability of standard test measurements as well as DIN, ISO and ASTM test parameters led to limitations and increased effort.

The motivation and main target to conduct the R&D project was to increase the consumer and operator safety by using unclassified (GHS) high performance lubricants. The findings of the project show clearly that the tasks could be fulfilled. Special, unclassified (GHS) selected white solid lubricants are able to form a reaction layer on metal surfaces and separate effectively the surfaces within the tribological system. No fretting wear accrued. The consumer can gain substantial benefits on the economical side as well as on the ecological side.

This paper aims to explore the leaf-surface wax as green lubricant additive and compare the tribological properties between coastal and inland leaf-surface waxes of the same species plant.

The leaf-surface waxes were extracted from the leaves of Robinia pseudoacacia cv. Idaho and Populus nigra in coastal and inland areas, and then the compositions of the four kinds of leaf-surface waxes were characterized using a gas chromatography–mass spectrometry. The tribological properties of these leaf-surface waxes as lubricant additives in the base oil of synthetic ester (SE) were investigated by an MFT-R4000 reciprocating friction and wear tester. As well as the surface morphologies and chemical compositions of the wear scars were characterized by a scanning electron microscope and time-of-flight secondary ion mass spectrometry, respectively.

The results indicate that all the leaf-surface waxes as additives can effectively improve the friction reduction and anti-wear performances of SE for steel–aluminum friction pairs. Therein, coastal leaf-surface waxes have better tribological performances than inland leaf-surface waxes, which are attributed to that the leaf-surface waxes extracted from coastal plants can form a better protective film on the worn surface throughout the friction process.

This paper investigated a new kind of environmentally friendly lubricant additive and compared the tribological properties of the leaf-surface wax extracted from coastal and inland plants. The associated conclusions can provide a reference to explore the tribological performances of leaf-surface wax as green lubricant additive.

The high density of defects mainly attributed to the presence of silicon oxycarbides, residual C clusters, Si- and C-dangling bonds at or near the SiO₂/SiC interface degrades the performance of metal-oxide-semiconductor (MOS) devices. In the effort of further improving the quality and enhancement of the SiC oxides thickness, post-oxidation annealed by a combination of nitric acid (HNO₃) and water (H₂O) vapor technique on thermally grown wet-oxides is introduced in this work. The paper aims to discuss these issues.

A new technique of post-oxidation annealing (POA) on wet-oxidized n-type 4H-SiC in a combination of HNO₃ and H₂O vapor at various heating temperatures (70°C, 90°C and 110°C) of HNO₃ solution has been introduced in this work.

It has been revealed that the samples annealed in HNO₃ + H₂O vapour ambient by various heating temperatures of HNO₃ solution; particularly at 110°C is able to produce oxide with lower interface-state density and higher breakdown voltage as compared to wet-oxidized sample annealed in N2 ambient. The substrate properties upon oxide removal show surface roughness reduces as the heating temperature of HNO₃ solution increases, which is mainly attributed due to the significant reduction of carbon content at the SiC/SiO₂ interface by C=N passivation and CO or CO₂ out-diffusion.

Despite being as a strong oxidizing agent, vaporized HNO₃ can also be utilized as nitridation and hydrogen passivation agent in high temperature thermal oxidation ambient and these advantages were demonstrated in 4H-SiC.

To study the influence of storage time and environment on the solderability of electroless nickel plated samples with Sn‐3.8Ag‐0.7Cu and Sn‐3.5Ag lead‐free solders and to provide criteria for the use of an electroless nickel (Ni‐P) under bump metallization (UBM) without immersion gold protection.

Electroless nickel coatings were deposited onto pure aluminium foil through a procedure developed for the UBM of wafers prior to flip chip bumping. Their solderability with lead‐free solders was studied using the wetting balance technique. Samples stored in different environments for different periods of time were tested to study the dependence of the solderability of Ni‐P coatings on the storage time and temperature. The degree of oxidation of the Ni‐P coatings was examined by means of X‐ray photoelectron spectroscopy and the surface microstructure and roughness of the coatings were analyzed by scanning electron microscopy and atomic force microscopy.

It was found that the Ni‐P coatings were unacceptable for direct soldering without the assistance of a flux, due to poor wettability, even when using a freshly prepared Ni‐P coating. Therefore, a suitable flux with nitrogen inerting had to be applied to assist the soldering process. The results also show that the solderability of Ni‐P coatings was affected by the phosphorus content, and the Ni‐P coating with high phosphorus content had a good solderability. The storage time and temperature did not influence the wettability significantly with the assistance of strong flux.

The stability of the plating solution and the consistence of the phosphorus content in the coating are not easily controlled. This has resulted in implications for surface analysis and wetting testing. Ni‐P coatings with different levels of phosphorus content are being investigated in detail.

The value of the paper lies in its study on the solderability of lead‐free solders to Ni‐P coating after storage in different environments and for different periods, which can provide some criteria for the use of Ni‐P UBM without immersion gold protection.

This paper aims to acquire the current density distribution on dissolving of Mg, MgZn₂ (η -phase), Mg₂Si (ß-phase) and Al₄Cu₂Mg₈Si₇ (Q-phase) surface in NaCl solutions.

MgZn₂ (η -phase), Mg₂Si (ß-phase) and Al₄Cu₂Mg₈Si₇ (Q-phase) are important intermetallic compounds found in aluminum alloys. Insitu scanning vibrating electrode technique (SVET) was used to acquire the current density distribution on dissolving of Mg, MgZn₂ (η -phase), Mg₂Si (ß-phase) and Al₄Cu₂Mg₈Si₇ (Q-phase) surface in NaCl solutions scanning electron microscopy/energy-dispersive X-ray spectroscopy (SEM/EDX) was used to characterize the corroded surface.

SVET maps reveal that these compounds display characteristic dissolution features. Mg and MgZn₂ displayed localized anodic and cathodic sites while that of Al₄Cu₂Mg₈Si₇ > Mg₂Si displayed a diffused distribution of anodic and cathodic sites. The magnitude of the integrated anodic current densities on the compounds was noted to decrease with the progress of time, and the order of the magnitude of the current density with respect to the compounds is Mg > Mg₂Si > Al₄Cu₂Mg₈Si₇ > MgZn₂. SEM/EDX reveal that the highest mass loss recorded after the SVET test was manifested by Mg₂Si followed by MgZn₂ then Al₄Cu₂Mg₈Si₇.

Auxiliary information on the current density distribution on the corroding sample surface at the microscopic scale has been provided by SVET thereby taking care of certain limitations of traditional corrosion monitoring techniques such as gravimetric, hydrogen evolution and electrochemical measurements.

This paper aims to report the first iteration on the Light Detection and Ranging (LIDAR) Engineering Model altimeter named HELENA. HELENA is a Time of Flight (TOF) altimeter that provides time-tagged distances and velocity measurements. The LIDAR can be used for support near asteroid navigation and provides scientific information. The HELENA design comprises two types of technologies: a microchip laser and low noise sensor. The synergies between these two technologies enable developing a compact instrument for range measurements of up to 14 km. Thermal-mechanical and radiometric simulations of the HELENA telescope are reported in this paper. The design is subjected to vibrational, static and thermal conditions, and it was possible to conclude by the results that the telescope is compliant with the random vibration levels, the static load and the operating temperatures.

The Asteroid Impact & Deflection Assessment (AIDA) is a collaboration between the NASA DART mission and ESA Hera mission. The aim scope is to study the asteroid deflection through a kinetic collision. DART spacecraft will collide with Didymos-B, while ground stations monitor the orbit change. HERA spacecraft will study the post-impact scenario. The HERA spacecraft is composed by a main spacecraft and two small CubeSats. HERA will monitor the asteroid through cameras, radar, satellite-to-satellite doppler tracking, LIDAR, seismometry and gravimetry.

The HELENA design comprises two types of technologies: a microchip laser and low noise sensor. The synergies between these two technologies enable developing a compact instrument for range measurements of up to 14 km.

In this paper is reported the first iteration on the LIDAR Engineering Model altimeter named HELENA. HELENA is a TOF altimeter that provides time-tagged distances and velocity measurements. The LIDAR can be used for support near asteroid navigation and provides scientific information. The HELENA design comprises two types of technologies: a microchip laser and low noise sensor. The synergies between these two technologies enable developing a compact instrument for range measurements of up to 14 km.

The paper aims to study comparatively the fretting behavior in gross slip regime of fretting both under grease lubrication and dry condition and to investigate the mechanism of palliation of fretting wear with grease lubrication.

All fretting tests were carried out on high‐temperature fretting devices with standard GCr15 bearing steel ball against 45 steel flat and against GCr15 bearing steel flat contact pairs. The wear scar was examined by optical microscope, surface profiler and the confocal laser scanning microscope as well as energy dispersive X‐ray spectroscopy.

Compared with dry condition, the coefficient of friction and wear are decreased drastically and wear occurs mainly at the early stage of fretting under grease lubrication. The palliation effect of grease lubrication is closely associated with the amount of oil separated from the grease, the low‐oxidation corrosion and high‐hardness white layer. However, the bubbles which expelled from the contact edges have little influence on fretting wear.

The tested greases do not contain any additives for preventing possible misinterpretations of the results, but it is necessary to investigate the influence of different lubricant additives added to grease on friction and wear at different fretting conditions.

The research reveals that the palliation effect of grease lubrication on fretting wear is related closely to the amount of oil separated from the grease. The bigger penetration and more susceptible greases, which are easier to separate from the base oil, should be taken into account for palliation of fretting wear.

The presented results help to understand the palliation mechanism of grease lubrication and could be useful for designers of engineering assembly for which fretting wear is an issue.

The purpose of this paper is to develop hybrid organic‐inorganic silica‐based nanocomposite films, by sol‐gel method, for corrosion protection of AA2024 alloy. Also, cerium nitrate corrosion inhibitor is introduced into the optimized coating in the next step of the investigations in order to study the improvement in the corrosion protection properties of the organically modified silicate (Ormosil) films.

The sol‐gel films have been synthesized from 3‐glycidoxypropyltrimethoxysilane and tetraethylorthosilicate precursors. In order to investigate the effective factors on the properties of Ormosils films, different coatings with different organic and hydrolysis water content were developed. Then, cerium nitrate corrosion inhibitor was added to the coatings. The structure of the hybrid sol‐gel films was studied by scanning electron microscopy. The corrosion protection properties of the films were studied by potentiodynamic scanning, and electrochemical impedance spectroscopy, respectively.

The results indicate that the hybrid films provided exceptional barrier and corrosion protection in comparison with untreated aluminium alloy substrate. Moreover, improvement of the protection properties of the films containing cerium nitrate corrosion inhibitor occurred with immersion time. This would imply that cerium ions could reach the defects, and reduce the corrosion rate.

This paper provides the development of Ormosils coating, which exceptionally improves the corrosion protection of 2024 aluminium alloy.

The objective of this paper is to study the effect of a commercial lubricant, which contains a 50‐50 mixture of zinc diamyldithiocarbamate and petroleum oil, on the fretting corrosion of tin‐plated copper alloy contacts.

The change in contact resistance as a function of fretting cycles was used to assess the effectiveness of the lubricant in preventing the fretting corrosion of tin‐plated contacts. The surface profile, surface roughness, extent of fretting damage and extent of oxidation of the contact zone were assessed by a laser scanning microscope and surface analytical techniques to correlate the change in contact resistance with fretting cycles.

The lubricant film provides a surface coverage of 6.76±1 mg/cm² and it easily establishes metallic asperity contact between the mated tin‐plated contacts. The contact resistance of lubricated contacts remains stable for several thousand fretting cycles. Lubricated contacts reach a threshold value of 0.1 Ω around 100,000 cycles, whereas unlubricated contact reaches this value around 13,500 cycles itself. For lubricated contacts, the extent of mechanical wear of the tin coating is significantly reduced. As a result, they experience a lesser damage at the contact zone and exhibit a smoother profile. The formation of tin oxide is not appreciable and there is no oxide accumulation at the contact zone even at 380,000 cycles. The lubricant is very effective in delaying the fretting wear during the initial stages and in preventing the oxidation and accumulation of oxidation products at the contact zone in the later stages.

Metallic dialkyldithiocarbamates are useful anti‐wear and extreme pressure additives for lubricating oils. Dithiocarbamates improve the antioxidant properties of the lubricants and are effective in reducing the wear and increasing the friction‐reducing and load‐carrying ability of the base stock. The use of molybdenum dithiocarbamate as a grease additive is found to be effective in reducing fretting corrosion of ball bearings under random rotary vibrating conditions. The effect of dithiocarbamate containing lubricant oils or greases on the fretting corrosion of electrical contacts has not far been studied. The paper explores the effect of a lubricant that contains a 50‐50 mixture of petroleum oil and zinc diamyldithiocarbamate on the fretting corrosion of tin‐plated contact.